The present invention concerns the focused ion beam machining of copper on substrates such as microelectronic substrates.
Focused ion beam machining (FIBM) is required for design debug, editing and verification, metrology, and process control of nanofabricated devices such as microelectronic substrates. See, e.g., U.S. Pat. No. 5,188,705 to Swanson et al., U.S. Pat. No. 6,140,655 to Russell et al., and U.S. Pat. No. 5,798,529 to Wagner et al.
Unfortunately, the current knowledge base associated with the FIBM of aluminum does not directly transfer to copper micro-machining. Copper is notoriously difficult to micro-machine uniformly with a focused ion beam since the micro-machining rate depends heavily on Cu grain orientation. J. Phillips et al., J. Vac. Sci. Technol. A 18, 1061 (2000); D. Thaus et al., J. Vac. Sci. Technol. B 14, 3928 (1996). Accordingly, there is a need for new ways to carry out the focused ion beam, or other particle beam, machining of copper.
A first aspect of the present invention is, accordingly, a method of micromachining a copper layer on a substrate. The method comprises: bombarding a portion of the substrate (particularly the copper layer) with a particle beam (e.g., a focused beam or charged particle beam) from a particle source; and exposing the substrate to a supply of organic chloride or organic hydroxide during particle bombardment, the organic chloride or organic hydroxide vapor concentration at the substrate being sufficient to enhance removal (including removal in whole or removal in part) of the copper layer. The substrate is preferably maintained in a vacuum during the bombarding and exposing steps. The vacuum need only be sufficient for achieving the intended purpose of micromachining the copper, and need not be absolute.
A second aspect of the present invention is a method of selectively removing a first, copper material from a substrate to expose a neighboring (underlying or adjacent) layer of a second material. The method comprises maintaining the substrate in a vacuum; bombarding with a particle beam (e.g., a focused beam or charged particle beam) a portion of the substrate having a first copper material neighboring a second material such as a dielectric; and exposing the portion of the substrate to an organic chloride or organic hydroxide during particle bombardment of the substrate, the first copper layer having a sputter etch rate that either 1) is increased by the presence of organic chloride or organic hydroxide vapor and the second material having a sputter etch rate that is not increased by the presence of organic chloride or organic hydroxide vapor to the degree that the sputter etch rate of the first material is increased, thereby selectively sputtering the first material compared with the second material; or is decreased by the presence of organic chloride or organic hydroxide vapor and the second material having a sputter etch rate that is decreased by the presence of organic chloride or organic hydroxide vapor to the degree that the sputter etch rate of the second material is decreased, thereby selectively sputtering the first material compared with the second material; or a combination of both. In one embodiment, the second material underlies the first material. In a particular embodiment, exposing the substrate to a supply of organic chloride or organic hydroxide includes exposing the substrate to organic chloride or organic hydroxide vapor at a partial pressure of approximately 1 mTorr. In one preferred embodiment, the particle beam comprises a beam of gallium ions focused to a sub-micron target point.
A further aspect of the present invention is a method of shaping features of a surface of a solid object having a surface. The method comprises the steps of: positioning the object within an enclosed chamber; supplying organic chloride or organic hydroxide vapor within the chamber so that organic chloride or organic hydroxide is adsorbed onto the exposed surface of the object for enabling a chemical reaction between the organic chloride or organic hydroxide and a copper layer at the surface; generating a particle beam (e.g., a focused beam or charged particle beam); and directing the beam toward the surface for removal by sputtering of a portion of the copper layer, the particle-beam induced chemical reaction between the organic chloride or hydroxide and the copper layer increasing the sputtering selectivity of the copper layer relative to the neighboring layer and especially the underlying layer.
A still further aspect of the present invention is a method of chemically-enhanced particle beam machining of a copper layer on a substrate for cross-sectional analysis. The method comprises maintaining a substrate in a vacuum; applying an organic chloride or organic hydroxide to the substrate; and bombarding with a particle beam (e.g., a focused beam or charged particle beam) a portion of the substrate including thereon a copper layer to expose for examination a cross section of the copper layer. The organic chloride or organic hydroxide is applied to the substrate at a concentration sufficient to enhance removal of the copper layer.
Still further aspects of the present invention include the products which may be produced by the processes described herein.
The present invention also provides a focused particle beam metrology device. The device comprises: a particle beam (e.g., a focused particle beam or charged particle beam) source which produces low intensity focused particle beams directed to a semiconductor device having features thereon; a detector which detects electrons or ions emitted from the semiconductor device; a processor which receives data from the detector and measures dimensions of the features from the data; a discharge device which introduces an organic chloride or organic hydroxide toward the semiconductor device (the device preferably including a copper layer as described herein); and a control device connected to the particle beam device to vary intensity of the focused particle beams for generating high intensity focused particle beams to etch the semiconductor device. Preferably the detector is located substantially above the semiconductor device for top-down linewidth measurements. The device may include a display device connected to the processor, wherein the display device displays an image of the semiconductor device. The high intensity focused particle beams may partly or completely etch through the semiconductor device. In one embodiment, the high intensity particle beams etch a crater in the semiconductor device exposing a cross-section of the semiconductor device, and the low intensity particle beams scan the cross-section at a predetermined angle to form an image of the cross-section. The device may further include a movable platform for holding the semiconductor device, wherein the movable platform is tilted at the predetermined angle during the low intensity particle beam scanning of the cross-section.
In a particular embodiment of the foregoing, the present invention provides a method of forming a three dimensional profile of a copper feature of a semiconductor device, the method comprising the steps of: introducing an organic chloride or organic hydroxide toward the semiconductor device through a discharge device; etching a top surface of the feature with a high intensity focused particle beam from an particle beam source; forming a top-down image of the top surface on an image forming device connected to a processor; repeating the etching and forming steps until the feature is completely etched from top to bottom to form successive top-down images of the etched feature; and overlaying the top-down images of the feature by the processor to form the three dimensional profile of the feature.
In another particular embodiment of the foregoing, the present invention provides a method of measuring a cross-section profile of a copper layer of a semiconductor device which comprises the steps of: introducing an organic chloride or organic hydroxide toward the semiconductor device through a discharge device; etching a crater to expose the cross-section by a high intensity focused particle beam generated from a first particle beam source; directing a low intensity particle beam toward the cross-section; and forming an image of the cross-section on an image forming device from low intensity particle beams generated from the particle beam source and reflected from the cross-section.